1. Field
The present application relates to wireless communications. More particularly, the present application relates to a method and apparatus for signal acquisition in peer-to-peer spread-spectrum communications.
2. Background
Mobile devices supporting spread-spectrum technologies, such as Code Division-Multiple Access (CDMA), typically require communication with a cellular base station prior to transmission. In a typical cellular communication, the base station provides a system time value, which may be thought of as an absolute time, to the mobile devices. The mobile devices are then able to use the system time for synchronization and other functions.
For example, normal reverse link communication between a mobile device and a CDMA base station relies on synchronization as follows. The base station uses the known timing of long and short pseudo-random noise (PN) spreading codes to despread received signals from a mobile device. This operation provides processing gain against interference and ensures that the demodulated signal is aligned with frame timing. In addition, the base station uses the known timing of the pseudo-random gating of reverse link transmissions to determine when a signal from a mobile device is present.